Whitelisting is a feature that enables data flows associated, e.g., with applications, emails, and data, generally, to traverse a network element, such as a router, switch or firewall, without further inspection or scrutiny. That is, when given traffic or a data flow is determined to be on a network element's whitelist, that traffic or flow is permitted to traverse the network element without requiring additional processing or overhead.
One form of whitelisting is Domain-based whitelisting. Domain-based whitelisting whitelists traffic flowing to/from selected domains and ensures that such traffic is not subjected to additional inspection. This type of whitelisting is implemented to avoid the overhead of inspecting selected flows that may not warrant inspection (e.g., YouTube™ or other video traffic), or to avoid inspecting traffic destined to/received from domains that carry sensitive information (e.g., personal banking traffic which may not be allowed, in certain countries, to be decrypted, even within an Enterprise network).